There are existing specifications which define the communications and operational support interface requirements for a data-over-cable system. One of these specifications is data over cable service interface specification (DOCSIS), an international standard which permits the addition of high-speed data transfer to an existing cable television (CATV) system and is employed by many cable television operators to provide Internet access over their existing hybrid fiber coaxial (HFC) infrastructure.
Cable modems based on solutions such as DOCSIS are expensive and are not suitable to provide a quality of service (QoS) that is sensitive to real time audio communication and video streaming services in cable networks. It is desirable to develop a new system to transmit data through a CATV cable access network which can guarantee good quality of service (QoS) and leverages off of existing standard protocols at a reasonable cost. A user-terminal device or modem which operates on an existing CATV system and provides internet-style data services to client devices, such as devices on a local area network, is also desirable in a cable data system. In such a system, multicasting to user-terminals would be an efficient method to distribute content to a multiplicity of user terminals that are to receive the same data. In multicasting, transmission data rates are usually fixed by the slowest receive rate of the members in a multicast group. But, the slowest rate user-terminal may change over time. Assigning a slowest, fixed data rate user-terminal approach to data rate transmission in a multicasting scheme may not accommodate changes in the user-terminals within the multicast group. Another factor is the access point. If the access point increases transmit power to some stations, the increased power may allow a higher data rate to the selected stations. A more efficient and adaptable data rate determination mechanism would be beneficial to bandwidth preservation in the cable system.